I am trying to configure Asterisk for BSNL, india network.
I have successfully configured it for outgoing calls.

Right now trunk is able to make any call to outside world and receive
any call from outside world. As when it makes any call to outside
world then it sends proper signals for ringing, disconnection, etc.
So outside world number will receive the call and when the call is
disconnected it notifies properly to outside number about call
disconnection.
But when any outside number make any call to trunk then it receives
the call properly but when the call is disconnected by outside number
then it fails to identify disconnection tone. So it shows as if the
line is connected even after disconnection from outside world call.

Outside number receives busy signal instead of disconnect tone.


My system information is as follows:

OS and components:

CentOS 4.5
Asterisk 1.4.17
Zaptel 1.4.7.1
Libpri 1.4.3

extensions.conf
[globals]
OUTBOUNDTRUNK=Zap/4

[incoming]
; incoming calls from FXO
exten => s,1,Dial(Zap/1)
exten => s,n,Hangup()

[internal]
exten => 500,1,Verbose(1|Echo test application)
exten => 500,n,Playback(hello-world) ;For testing the extension, it
will ;play "hello world"
exten => 500,n,Hangup()

[outbound-dialing]
;Outbound dialing
exten => _X.,1,Verbose(1|Outside number|${EXTEN})
exten => _X.,n,Dial(${OUTBOUNDTRUNK}/${EXTEN})

[phones]
include => internal
include => outbound-dialing

zaptel.conf file:

fxsks=4
fxoks=1
loadzone=uk
defaultzone=uk

# /sbin/ztcfg -vv this linux command gives following output:
Zaptel Version: 1.4.7.1
Echo Canceller: MG2
Configuration
======================

Channel map:

Channel 01: FXO Kewlstart (Default) (Slaves: 01)
Channel 04: FXS Kewlstart (Default) (Slaves: 04)

2 channels to configure.

zapata.conf file looks like:
[trunkgroups]
; Define

[channels]
;hardware channels
;default
usecallerid=yes
hidecallerid=no
callwaiting=no
threewaycalling=yes
transfer=yes
echocancel=yes
echotraining=yes
immediate=no
cidstart=ring
cid_signalling=dtmf

;define channels
signalling=fxo_ks ;Use FXO signaling for FXS channel
context=phones
channel => 1

signalling=fxs_ks ;Use FXS signaling for FXO channel
busydetect=yes
busycount=6
busypattern=0,750
hanguponpolarityswitch=yes
callprogress=no
progzone=uk
ringtimeout=8000
context=incoming
channel => 4

I found following disconnection tone string:

400@-30,400@-30;4(.8/.8/1+2)

on this forum for bsnl india network.
But I don't know where to put this string in configuration files. And
whether this string will be helpful for me or not.

Any sort of help will be appreciated.

Thanks in advance

Prashant